Light hydrocarbon distillation



July 16, 1935. s COOKE 2,008,578

LIGHT HYDROCARBON DISTILLATION Filed May 17, 1930 36 Uapons.

. Euler Condenser Goolin water-- Factiona Gas Outomas 5- Coolie PatentedJuly 16, 1935' UNITED STATES 2,008,578 7 'LIGHT' HYDROCARBONDISTILLATIONT poration of Indiana Thomas S. Cooke, East Orange, N. J.,assignor to Standard Oil Company,

Chicago, 111., a cor- Application May 17, 1930, Serial No. 453,374

Claims.

This invention relates to an apparatus and process for distillinghydrocarbon vapors, and it pertains more particularly to thedistillation of pressure distillate by'the use of naphtha vapors.

Many oil refineries are located in arid regions where water is scarce.An object of my invention is to provide a process and apparatus fordistillation which will avoidthe necessity of supplying fresh water andwhich will avoid the necessity of an extensive investment in steamboilers and accessory equipment for furnishing steam.

A further object is to provide a process in which pressuredistillate'may be re-distilled at a ternperature low enough to obtain adistillate of satisfactory color.

A further object is to utilize the finishing distillation of corrosiveor discolored naphtha for efiecting distillation of cracked gasoline sothat the resulting product will be of satisfactory color and stability.

Other objects will be apparent as the detailed description of myinvention proceeds.

My invention contemplates a continuous cyclic process wherein preheatedpressure distillate is stripped in a fractionating tower by naphthavapors from a flash drum, the naphtha being mixed with the refluxleaving the fractionating tower before it enters the pipe still. I mayuse corrosive or off color naphtha for this purpose, or I may use aportion of the naphtha which is obtained by condensing the vaporsleaving the fractionating tower. My invention will be more clearlyunderstood from the following detailed description:

In the accompanying drawing I have diagrammatically illustrated anapparatus suitable for carrying out my improved process.

The feed stock which is preferably pressure distillate or crackedgasoline is pumped from any suitable source through pipe ID to preheatercoil H in condenser .12. The preheated stock is then led by pipe I 3 toan intermediate point of fractionating tower Id at which point thedistillate is discharged above a stripping section 15. The stripped feedstock is conducted from the base of the fractionating tower by pipe IEto pump H, which forces it through pipe 18 to heating coil H3 in pipestill 20. Before entering the pipe still the feed stock is mixed withnaphtha, as 50 will be hereinafter described.

The hot mixture of naphtha and feed stock is conducted by pipe 2| toflash drum 22, which is provided with means for effectively separatingthe naphtha vapors from the bottoms or residues which are withdrawnthrough pipe 23. The

naphtha vapors are conducted by pipe 24 to the bottom of fractionatingtower [4 wherein they pass counter-current to the incoming feed stockand act as a strippingmedium therefor. The non-volatilized feed stockand condensed vapors are re-circulated through the pipe still as abovedescribed, and the c'ombined'vapors are passed through the upper sectionof the fractionating tower which may be equipped with suitable bubbleplates 25,and are then conducted by pipe 26 to condenser !2. After thevapors have given up substantially all of their heat to the incomingfeed stock they are further cooled by coil 21 wherein a cooling fluid iscirculated. a

The gases and liquids are led by pipe 28 from E5 the condenser to a gasrelease drum 29, non-condensed gases passing by pipe 30 to a suitableabsorption plant or to a furnace, and the finished naphtha beingwithdrawn through pipe 3 l.

Part of the finished product may be withdrawn through valve 32 and pipe33 to a storage tank and part may be re-circulated through valve 34,pipe 35, pump 35 and pipe 3'! back to the pipe still for distillingfurther amounts of incoming feed stock. r

If unstable, corrosive, or off color naphtha is available, it may beintroduced through pipe 38, valve 39, pump 35 and pipe 31'. Suchunfinished naphtha must be re-run for improving its color, stability orother properties, and its use in my improved process serves the doublefunction of rerunning or finishing the naphtha and stripping thepressure distillate.

The amount of naphtha introduced will, of course, depend upon thespecific distillate; in the particularcase of the cracked gasolinerefined from Venezuelan crude, a still producing finished gasoline atthe rate of 4,000 barrels per day requires about 25 gallons per minuteof a naphtha having an initial boiling point of F. and an end point of385 F. The ratio of stripping naphtha to charging stock is in this case,therefore, about one to six.

In re-distilling cracked gasoline which has been heavily treated withacid for the removal of sulfur, I have found that in order to obtaindistillate of satisfactory color the temperature must be kept below 485F. The methods heretofore used, vacuum distillation or distillation inthe presence of steam, require a large amount of apparatus, boilers andother equipment and would require large amounts of fresh water. By myimproved process I effect a saving in both of these items and at thesame time I obtain a distillate of superior steam and under conditionswhich substantially preclude cracking, which comprises stripping themwith volatilized normally liquid naphtha fractions in a tower,condensing the vapors leaving said tower, mixing a portion of theresulting condensate with the stripped oil, heating the mixture in aconfined stream to a temperature high enough to effect vaporization ofthe light fractions without cracking, separating the vapor- 'izedfractions from the residuum in a flash chamher, removing the liquidresiduum from said chamber, and introducing the separated vaporizedfractions as said volatilized normally liquid naphtha into the bottom ofthe tower and below the surface of the liquid oils therein.

2. The method of distilling hydrocarbon oils,

the preponderating portion of which is in-the naphtha range, without thesubstantial use of steam and up or conditions which substantiallypreclude cracking, which comprises stripping said oilswith unfinishednaphtha vapors, condensing the said naphtha vapors; mixing the strippedoil with a part of the resultant condensate, heating the mixture tovaporize the naphtha, separating the naphtha vapors from the unvaporizedresiduum, and using said vapors in said stripping step as saidunfinished naphtha vapors whereby the finishing of the naphtha isaccomplished simultaneously with the distillation of the oil.

3. The method of distilling hydrocarbon oils,

the preponderating portion of which is in the naphtha range, without thesubstantial use of steam and under conditions which substantiallypreclude cracking, which comprises introducing said hydrocarbon oilsinto a stripping tower, con-- 1 densing the vapors taken overhead from,said tower, separately withdrawing the stripped residuum from saidtower, mixing a portion of the resultant condensate from the overheadwith the stripped residuum and heating the mixture under non-crackingconditions in a confined stream to a temperature high enough to effectvaporization of the light fractions, separating the vaporized fractionfrom the bottoms by flashing, withdrawing the unvaporized bottoms fromthe flash zone,

separately withdrawing the vapors from the flash zone and introducingsaid vapors intothe strip-' ping tower for stripping the hydrocarbon'oils.

therein. i

4. The method of distillinghydrocarbon oils, the preponderating portionof which is in the naphtha range, which comprises stripping said oilwith unfinished naphtha. vapors, condensing the said naphtha vapors in azone remote from the zone in which the stripping takes place, mixing thestripped oil with some of the naphtha condensate, heatingthe mixture inaconfined stream without substantial cracking, separating unfinishednaphtha vapors from the liquid residuum, and using said vapors as theunfinished naphtha vapors in'the stripping step wherebythe finishingofthe naphtha is accomplished simultaneously with the distillation of theoil.

5. The method of distilling hydrocarbon oils, the preponderating portionof which is the naphtha range, which comprises stripping them withvolatilizednormally liquid naphtha fractions in a tower, condensing thevapors after leaving said tower, mixing a portion of said condensedvapors with the stripped oils, heating the mixture in a confined streamin a still without substantial cracking and to a temperatur'e'highenough to effect'vaporization of the light fractions from the liquidresidue in an enlarged chamber, removing the residue from said chamberand introducing the said separated vaporized light fractions as thevolatilized normally liquid naphtha into the tower for stripping thehydrocarbon oils therein.

THOMAS s. (300KB,

